It is known that the plants for the production of bituminous membrane rolls comprise in the end part of the roll production line: a roll forming station that receives a flat bituminous belt and winds it around a winding axis to form the finished membrane roll, and a palletization station that receives the finished bituminous membrane rolls and arranges them in ordered, parallel and adjacent positions, ready for the packaging.
Generally, in the aforesaid plants, the movement of the bituminous membrane rolls from the roll forming station to the palletization station is carried out through a conveyor. The conveyor comprises a support frame, a belt looped about rollers rotatably pivoted on the frame, and a handling assembly that rotates the rollers so as to advance the upper branch of the roll supporting and transporting belt towards a preset feeding direction.
In the known conveyors described above, the belt is made of a high-hardness rigid rubber, is seamlessly wound to form a closed loop and is kept stretched between the rollers to form on the upper transport branch a flat and rigid roll transport surface.
In the plants described above it happens that, in use, the rolls arranged on the transport surface of the upper branch of the belt tend to become remarkably oval during the advancement. In fact, when the roll is laid on the flat and rigid supporting surface of the belt, it is not completely cooled but is still partially soft because it still has a remarkably high temperature. Since it is not completely rigid, the roll tends both to deform in its lower supporting surface portion, which partially tends to flatten against the flat and rigid conveyor surface of the belt, and to be compressed, due to the weight force, towards the same, thus remarkably altering its original cylindrical section obtained in the roll forming station. Furthermore, studies carried out by the Applicant have shown that the oval effect also depends on the ambient temperature and on the bituminous compound used. In particular, it has been found that the deformation is enhanced both in the summer season and when the membrane mixture is made of particularly “soft” materials, such as styrene-butadiene-styrene.
The ovalization of the roll determines various problems. First, an oval roll is subject to instability problems when it is arranged vertically alongside other rolls during the palletization operation. Moreover, the oval roll is inconvenient for the installer, since during its application on flat surfaces, for example roofs, its not perfectly circular shape makes it hop, thus causing some improper misalignments with respect to the expected position.
The Applicant has therefore conducted an in-depth study aimed at identifying a conveyor that is able to transport the rolls of bituminous membrane without causing their ovalization.